Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 300428
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
1028 PM MDT SAT AUG 29 2015

.SYNOPSIS...A PACIFIC NORTHWEST STORM SYSTEM WILL BRING A COLD
FRONT INTO NORTHERN AND CENTRAL UTAH SUNDAY AND SUNDAY NIGHT. A
DRIER WEST TO SOUTHWEST FLOW WILL THEN DEVELOP FOR THE EARLY PART
OF THE UPCOMING WEEK.

&&

.DISCUSSION...AS AN UNSEASONABLY STRONG TROUGH APPROACHED THE
PACIFIC NORTHWEST THIS EVENING...THERE WAS A BRIEF PERIOD OF
SOMEWHAT ROBUST CONVECTION ACROSS NORTHERN BOX ELDER COUNTY. THIS
CONVECTION OCCURRED ALONG AN AXIS OF HIGHER PRECIPITABLE WATER
VALUES...COMBINED WITH SIGNIFICANT DEEP LAYER SHEAR. INSTABILITY
WAS QUITE LIMITED...WITH MLCAPE VALUES AROUND 200-500 J/KG AT
THEIR HEIGHT. THIS CONVECTION HAS LARGELY DIMINISHED WITH THE LOSS
OF THE HEATING OF THE DAY AND ADDITIONAL STABILIZATION. A FEW
SHOWERS OR PERHAPS AN ISOLATED THUNDERSTORM COULD STILL OCCUR FOR
THE NEXT SEVERAL HOURS BUT THE MAIN THREAT HAS ENDED.

OUTSIDE OF NORTHERN UTAH...LITTLE ADDITIONAL THREAT OF
PRECIPITATION EXISTS. UPDATED THE FORECAST TO REMOVE POPS FROM
MOST OF THE CWA...WITH THE PREVIOUSLY MENTIONED LOW POPS
REMAINING CLOSE TO THE IDAHO/UTAH BORDER. NO ADDITIONAL UPDATES
ARE ANTICIPATED.

PREVIOUS DISCUSSION FOLLOWS...

UPPER LEVEL RIDGE OVER THE GREAT BASIN THIS AFTERNOON AS AN
UNSEASONABLY STRONG TROUGH MOVES INTO THE PACIFIC NW. SOUTHWEST
FLOW HAS INCREASED OVER UTAH TODAY AHEAD OF THIS TROUGH RESULTING
IN BREEZY CONDITIONS ACROSS THE AREA. AN AXIS OF HIGHER
PRECIPITABLE WATER VALUES HAS SPREAD NORTH INTO WESTERN AND
CENTRAL UTAH. RELATIVELY MODEST SBCAPE EXTENDS NORTHWARD THROUGH
WESTERN UTAH SUPPORTING ISOLATED CONVECTION. ALTHOUGH THERE IS
SOME STRONGER DEEP LAYER SHEAR ACROSS THE NORTHWEST PORTION OF THE
STATE DO NOT ANTICIPATE MUCH STORM ORGANIZATION. WITH VIGOROUS
FLOW ALOFT AND DEWPOINT DEPRESSIONS OF GREATER THAN 40 DEGREES F
ANTICIPATE THAT SOME SHOWERS AND STORMS MAY PRODUCE STRONG WINDS.

AS THE TROUGH MOVES INLAND THE MOISTURE AXIS SHIFTS INTO EASTERN UTAH
ON SUNDAY WITH PRECIPITABLE WATER VALUES IN EXCESS OF .75". COLD
FRONT IS EXPECTED TO MOVE INTO NORTHWEST UT ON SUNDAY WITH SHOWERS
AND STORMS DEVELOPING ACROSS CENTRAL AND EASTERN UTAH FOR THE
AFTERNOON AND EVENING. AHEAD OF THE BOUNDARY EXPECT BREEZY
SOUTHWEST WINDS TO CONTINUE. TEMPERATURES ACROSS NW UT WILL BE
ABOUT 10 DEGREES F COOLER THAN TODAY WITH MAX TEMPS ACROSS THE
SOUTH DIPPING BY AROUND 5 DEGREES.

FRONT PUSHES INTO CENTRAL UT SUN NGT BEFORE STALLING OUT. THE
AIRMASS DRIES OUT BEHIND THE BOUNDARY...SO ONLY ANTICIPATE MINIMAL
TERRAIN DRIVEN CONVECTION IN THE MOST FAVORED LOCATIONS ON MONDAY.
SOUTH FLOW INCREASES AGAIN ON TUE AS ANOTHER TROUGH BEGINS TO MOVE
INTO THE PACIFIC NW. CORRESPONDING WITH THE INCREASED SOUTHERLY
FLOW IS A REBOUND IN TEMPERATURES FOR TUESDAY.

&&

.AVIATION...SOUTHERLY WINDS SHOULD PERSIST AT THE SLC TERMINAL
THROUGH AT LEAST 12Z...AND COULD BE GUSTY AT TIMES OVERNIGHT. A COLD
FRONT WILL SWITCH WINDS TO THE NORTHWEST SUNDAY...WITH THE MOST
LIKELY TIME FRAME OF 15Z TO 18Z. THERE IS ALSO A 20 PERCENT CHANCE
OF SHOWERS OR THUNDERSTORMS IMPACTING THE TERMINAL THROUGH THE TAF
PERIOD.

&&

.FIRE WEATHER...A COLD FRONT MOVES INTO THE NORTHWEST PORTION OF
THE STATE ON SUNDAY AND MOVES INTO CENTRAL UT SUN NIGHT BEFORE
STALLING OUT. AHEAD OF THIS FRONT ANTICIPATE BREEZY SOUTHWEST
WINDS ALTHOUGH MINIMUM RELATIVE HUMIDITY VALUES WILL BE WELL ABOVE
CRITICAL LEVELS. AHEAD OF THE FRONT SCATTERED SHOWERS AND
THUNDERSTORMS ARE EXPECTED ACROSS CENTRAL AND EASTERN UTAH. WINDS
DECREASE A BIT FOR MONDAY BEFORE INCREASING AGAIN ON TUESDAY AS
ANOTHER STORM SYSTEM MOVES INTO THE PACIFIC NW. ANTICIPATE LOCALLY
CRITICAL CONDITIONS ACROSS WEST CENTRAL AND NW UTAH ON TUE AND
WED.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&

$$

KRUSE/SCHOENING/GRAHAM/TRAPHAGAN

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)


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